Expandable impeller pump

ABSTRACT

An impeller includes a hub, and a plurality of blades supported by the hub, the blades being arranged in at least two blade rows. The impeller has a deployed configuration in which the blades extend away from the hub, and a stored configuration in which at least one of the blades is radially compressed, for example by folding the blade towards the hub. The impeller may also have an operational configuration in which at least some of the blades are deformed from the deployed configuration upon rotation of the impeller when in the deployed configuration. The outer edge of one or more blades may have a winglet, and the base of the blades may have an associated indentation to facilitate folding of the blades.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/227,277, filed Sep. 15, 2005, and claims the benefit of the filingdate of U.S. Provisional Patent Application No. 60/610,938, filed Sep.17, 2004, the disclosures of which are hereby incorporated by referenceherein.

BACKGROUND OF THE INVENTION

The present invention relates to fluid pumping impellers, in particularto expandable impellers.

Conventional impellers are manufactured with a particular bladeconfiguration, and significant deformation of the blades is generallyundesirable. Conventionally, the impeller has the same configurationduring storage, movement to its operating location, and use. However,there are situations where access to the operating location is through arestricted space, or space is otherwise at a premium during storage ortransport of the impeller, in which case the use of conventionalimpellers can be problematic.

SUMMARY OF THE INVENTION

An apparatus according to one embodiment of the present invention forinducing motion of a fluid relative to the apparatus includes animpeller. The impeller includes a hub extending in a length direction;and a plurality of blades supported by the hub, each blade having aproximal end attached to the hub and a distal end, the blades beingarranged in at least two blade rows arranged in series in the lengthdirection of the hub. The impeller has a deployed configuration and astored configuration, each blade in the deployed configuration extendingaway from the hub, and at least one of the blades in the storedconfiguration being compressed as to move the distal end of the at leastone blade towards the hub. Each blade row may include at least twoblades. Furthermore, the plurality of blades may be formed integrallywith the hub.

The distal end of at least one of the plurality of blades may include awinglet. In some embodiments, the distal end of each blade in at leastone blade row may include a winglet. In other embodiments, the distalend of each of the plurality of blades may include a winglet.

Preferred embodiments of the present invention may further include anexpandable sleeve. The sleeve may include a matrix and a film disposedaround the matrix, at least part of the impeller being located withinthe sleeve. The matrix may be formed from a shape memory material, andthe film may include an elastic polymer. The expandable sleeve may havea storage configuration and an expanded configuration. In the storageconfiguration, the sleeve may have a diameter less than about 4 mm. Thesleeve may have an inlet end and a discharge end, with a plurality ofvanes arranged at the discharge end. Each of the plurality of vanes mayhave an airfoil-shaped cross-section.

An apparatus according to another embodiment of the present inventionfor inducing motion of a fluid relative to the apparatus includes animpeller. The impeller includes a hub extending in a length direction;and a plurality of blades supported by the hub, each blade having aproximal end attached to the hub and a distal end, the blades beingarranged in at least two blade rows arranged in series in the lengthdirection of the hub. The impeller has a deployed configuration, astored configuration, and an operational configuration. Each blade inthe deployed configuration of the impeller extends away from the hub; atleast one of the blades in the stored configuration of the impeller iscompressed so as to move the distal end of the at least one bladetowards the hub; and at least some of the blades in the operationalconfiguration are deformed from the deployed configuration upon rotationof the impeller when in the deployed configuration.

The impeller may have a first radius in the deployed configuration and asecond radius in the stored configuration which is less than half thefirst radius. The impeller may also have a third radius in theoperational configuration, the second radius being less than half thethird radius. In preferred embodiments, the impeller in the operationalconfiguration may be operable to pump about 4 liters of fluid perminute.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show an impeller in the deployed and storedconfigurations, respectively;

FIG. 2 schematically illustrates deployment of an impeller;

FIG. 3A illustrates an impeller in a stored configuration, within astorage sleeve;

FIG. 3B illustrates an impeller self-deploying after emerging from astorage sleeve;

FIG. 4 illustrates deployed and operational configurations of animpeller;

FIG. 5 illustrates an impeller design having a low Reynolds number;

FIGS. 6A and 6B illustrate an impeller having three blade rows;

FIGS. 7A and 7B illustrate an impeller blade having a winglet;

FIGS. 8A-8C illustrate possible winglet configurations;

FIG. 8D illustrates possible winglet edge geometries;

FIGS. 9A-9D illustrate an end view of an impeller blade, furtherillustrating possible winglet configurations;

FIGS. 10A and 10B illustrate a blade having a trench around theproximate end of the blade;

FIG. 11 is a photograph of a molded polymer impeller;

FIG. 12 shows a stress-strain curve for an impeller blade material; and

FIG. 13 shows normalized average fluid shearing stress as a function oftip gap sizes.

DETAILED DESCRIPTION

An impeller according to an embodiment of the present inventioncomprises a hub, and at least one blade supported by the hub.Embodiments of the present invention include impellers having at leastone flexible blade, the impeller having a deployed configuration inwhich the blade extends away from the hub, and a stored configuration inwhich the impeller is radially compressed. For example, the blade may befolded in towards the hub, and held there by a storage sleeve such as ametal tube or cannula. In the stored configuration, the distal end ofthe blade is closer to the hub than in the deployed configuration, andthe radius can be significantly less, such as less than half that of theradius in the deployed state. The sleeve may comprise a non-expandableportion, in which the impeller is stored, and an expandable portion,into which the impeller can be moved for deployment. The impellerdeploys within the expanded portion of the sleeve.

Impellers according to the present invention may comprise a plurality ofblades, arranged in blade rows. The blade rows may be spaced apart alongthe hub, each blade row including one or more blades. For example, eachblade row may comprise two or three blades. Achieving the storedconfiguration is facilitated by providing multiple blade rows, ratherthan, for example, a single long blade curving around the hub. A singlelong blade can be considerably more difficult to fold in towards thehub.

Embodiments of the present invention may further include a sleeve, atleast part of the impeller being located within the sleeve, and thefluid flowing through the sleeve when the impeller rotates. The sleevemay be expandable, the sleeve having an expanded configuration when theimpeller is in the deployed configuration, and a stored configurationwhen the impeller is in the stored configuration. The sleeve may act toconstrain the impeller in the stored configuration. Alternatively, aseparate storage sleeve may be provided, with the impeller andexpandable sleeve both expanding when pushed out of the storage sleeve.An expandable sleeve may comprise a metal framework, for examplecomprising a shape memory alloy. An elastic polymer film may be disposedover the metal framework. Impeller blades may have a winglet at thedistal end of the blade, the winglet and the sleeve providing ahydraulic bearing for rotation of the impeller. For example, the sleevemay have a cylindrical inner surface inside which the impeller rotates,the fluid flowing through the sleeve, with the winglet of each blademoving proximate to the cylindrical inner surface as the impellerrotates, the fluid between the winglet and cylindrical inner surfaceforming the hydraulic bearing for rotation of the impeller.

An impeller may be stored in a storage sleeve, and deployed in a fluidpipe, through which fluid flows when the impeller is rotated. Thestorage sleeve may have a diameter approximately equal to or less thanhalf the diameter of the fluid pipe. The storage sleeve may be a metaltube in which the impeller is stored prior to deployment. The fluid pipemay be a utility pipe (water, gas, sewage, and the like), bodily vessel(such as a blood vessel), portion of a thrust unit for a vehicle, orother structure through which a fluid may flow. The impeller may beconveyed to a desired location in a stored configuration, thenself-deploy to an expanded, deployed state. The stored configurationfacilitates conveyance of the impeller to the desired location, enablingit to be passed through openings less than the diameter of the deployedstate.

The fluid pipe may be an expanded form of the storage sleeve, expansionof the storage sleeve allowing the impeller to deploy. In this case, theimpeller does not need to be pushed out of the sleeve to achieve thedeployed configuration. For example, an impeller according to an exampleof the present invention can be inserted in the stored configurationthrough a small entrance hole into a pipe of larger diameter. Theimpeller can be deployed by causing the impeller to move out of thestorage sleeve using the drive shaft. The impeller then unfolds into thedeployed state using stored strain energy in the blade material.

Rotation of the impeller may further change the blade configuration toan operating configuration. An impeller may have flexible blades thatdeform into an optimized hydrodynamic shape when rotating and operatingunder design load conditions.

Embodiments of the present invention include impellers having at leastone blade having a winglet. In the operating state, the winglet canimprove hydrodynamic performance of the impeller and reduce shearstresses that exist within the fluid. Impellers may include a pluralityof blades that facilitate the folding of the blades into the storagestate. The blades may be arranged in a plurality of rows of blades thatfacilitate the folding of the blades into the storage state, comparedwith folding a single blade extending a similar distance along the hub.The blades and (optionally) the hub may be constructed of a low modulusmaterial such as a polymer. The impeller can be a unitary structure,with the blades and impeller formed from the same material, for exampleby molding a polymer.

An impeller with a plurality of blade rows also facilitates the input oflarge values of fluid head or pressure rise. The specific speed of anaxial flow impeller according to the present invention may be comparableto the specific speed of mixed flow pumps.

An impeller can be inserted into a pipe in a folded state andsubsequently deployed. The impeller, when deployed in a fluid flow pipe,may further deform into an operating configuration when the fluid isbeing pumped by impeller rotation. At the end of the operation of theimpeller, the impeller can be radially compressed back into the storedconfiguration, for example by re-folding the flexible blades, andextracted through an entrance hole having a diameter less than that ofthe fluid pipe or deployed configuration. For example, the blades can berefolded and the impeller extracted into a cylindrical storage cavity bymeans of an attached rotary drive shaft or guide wire.

An impeller according to the present invention can operate in a lowReynolds number pipe flow, where the pipe boundary layer comprises amajority of the flow in the pipe. The Reynolds number of the relativeflow over the blades can be low, compared to conventional impellers andpumps.

The impeller can be optimized to operate in a non-Newtonian fluid. Theimpeller can be optimized to operate in a fluid containing delicateparticles (such as emulsion droplets, cells, and the like) that aredamaged by excessive shearing stress in the fluid. The impeller can bedesigned so that the operational configuration is optimized, notnecessarily the same as the deployed configuration under no loading.

An impeller with an indentation in the hub about the blade root can havereduced internal mechanical stresses within the blades when in thestored configuration. The indentation may also be used to further reducefluid shear stress induced by the impeller in the operating state.

The blades can be formed from polymer materials, such as polyurethane. Apolymer, such as polyurethane, having a modulus of 10,000 psi can beused. In some examples, the blades may have a stiffness approximatingthat of a thick rubber band. Hence, the blades have some stiffness butwill deform under operating load. For example, the material can bechosen so as to have a linear modulus at operational stresses, allowingpredictable deformation under load, and a non-linear modulus at thehigher stresses used to fold the blades into the stored configuration.

FIG. 1A shows an impeller in a deployed configuration, the impellercomprising a hub 10 and blades such as blade 12. The impeller has aradius R₁, as measured from the central long axis of the hub to theoutermost blade tip. Also shown is a fluid flow sleeve 14, through whichfluid flows relative to the impeller. The impeller may be used as anaxial pump, to pump fluid through the sleeve. Alternatively, theimpeller may be used as a motive force provider for a vehicle. Forexample, the impeller may power a boat, such as a jet-boat, or otherwater craft, the sleeve being a tube immersed in the water surroundingthe vehicle. In this configuration, the blades are deployed.

FIG. 1B shows the impeller in a stored configuration, with blade 12folded or otherwise deformed towards the hub 10. The radius R2 is lessthan the radius R₁ shown in FIG. 1A.

An impeller according to an embodiment of the present invention hasflexible blades 15 that can be folded such that the maximum diameter ofthe impeller in the folded state is approximately half, or less thanhalf, the diameter of the impeller in the operating state. Referring toFIGS. 1A and 1B, this corresponds to R2≈≦(R₁/2).

FIG. 2 is a schematic diagram illustrating deployment of the impeller.The impeller has hub 20 and blades such as 22, and is retained in thestored configuration by storage sleeve 24. A rotating shaft 30 is usedto drive the impeller. The figure also shows a guide wire 28 within therotating shaft, which can be used to position the impeller, and also tohelp push the impeller out of the storage sleeve. The storage sleeve maybe, for example, a metal tube. Rotation of the shaft may also assistdeploying the impeller, for example through twisting the impeller out ofthe storage sleeve if the inner surface of the storage sleeve has athreaded texture. On the left, a fluid pipe 26 is shown, through whichfluid flows when the impeller is deployed and rotated.

An impeller in the stored configuration can be stored in a cylindricalcavity formed by storage sleeve 24 of diameter approximately equal to orless than half the diameter of the fluid pipe 26.

The storage sleeve may be a metal tube in which the impeller is storedprior to deployment. The fluid pipe 26 is any structure through which afluid may flow relative to the impeller, such as a tube or bodilyvessel. The impeller may be conveyed to the desired location within thefluid pipe in the stored configuration, then self-deploy to an expanded,deployed state. The stored configuration allows the impeller to passthrough openings having an area less than the area of the deployedstate, as swept out by the rotating blades.

Alternatively, the fluid pipe 26 may be an expanded form of the storagesleeve 24, expansion of the constraining sleeve allowing the impeller todeploy. In this case, the impeller does not need to be pushed out of thesleeve to achieve the deployed configuration. For example, an impellercan be inserted into a fluid pipe through a smaller hole, such as asmaller branch pipe or hole in the pipe wall. The impeller can then bedeployed by causing the impeller to move out of the storage sleeve usingthe drive shaft. Deployment may occur without any outside energy input,using stored strain energy in the blades when the blades are in thestored configuration.

FIG. 3A further illustrates an impeller in a stored configuration,showing blades such as blade 34, and hub 30. The blades are kept foldedagainst the hub by the storage sleeve 36. FIG. 3B shows the impellerpushed out of the storage sleeve and self-deployed. The impeller has tworows of blades, as is seen more clearly in the deployed state, the firstrow including blade 34 and the second row including blade 32.

FIG. 4 shows an impeller comprising hub 60 and a plurality of blades,the blades being shown in both the deployed and operatingconfigurations. The deployed configuration is the blade configurationunder no load, and the operating configuration is the configuration whenthe impeller rotates at the operational rotation speed. The blades areshown at 62A, 64A, and 66A for the deployed configuration. When underload, such as rotating in a fluid, the blades deform to an operationalconfiguration, with the blades at 62B, 64B, and 66B. Rotation of theimpeller changes the blade configuration from the deployed configuration(for no load) to an operating configuration. The flexible blades candeform into an optimized hydrodynamic shape when rotating and operatingunder design load conditions.

FIG. 4 compares the deployed blade shape with the operating blade shape.For a hub and blades formed from the same polymer, simulations showedthat the hub also deflects slightly in a rotational manner, as thesecond blade row is rotated at the root compared to the first blade row.In general, the blades deflect forward as the lift on the blades is suchthat they create thrust, a force directed towards the left side of thefigure, moving the blades toward the right side of the picture. Theleading edge of the second blade row is obscured. There are two bladerows, each with two identical blades.

Blade shapes can be optimized using standard computational fluiddynamics analysis (CFD). However, conventionally, the non-rotating,non-loaded configuration is optimized. (If the impeller is notexpandable, the deployed shape is the shape of the impeller when notrotating, and there is no stored configuration). An improved impellerhas an optimized operational configuration, and an improved method ofdesigning an impeller includes optimizing the operational configuration.A structural computation determines an allowance for deformation underload from the deployed state.

FIG. 5 illustrates an impeller design having a low Reynolds number. Theimpeller comprises hub 80, and two rows of blades having two bladeseach. The first row includes blades 82 and 84, and the second rowincludes blades 86 and 88.

This illustration shows the design elements of a low Reynolds numberimpeller, where the thickness of the boundary layer on the fluid pipewalls is as thick as the diameter of the pipe. The impeller has highlycurved leading and trailing edge lines where the blade pitch angles areadjusted for the local values of relative flow angle. The second rowblades have a groove-like feature that takes a helical path from theleading edge to the trailing edge. This is due to variations in thespanwise loading, and allows an axial flow pump using this impeller toachieve a head rise similar to that of a mixed flow pump. The middle ofthe span of the blade is relatively highly loaded, leading to thisfeature. The second row blades may be further split into two separatedblade rows, and this general feature will still present but not soapparent.

FIGS. 6A and 6B illustrate end and side views of an impeller,respectively. The impeller comprises hub 100, a first row of bladescomprising blades 102 and 104, a second row of blades comprising blades106 and 108, and a third row of blades comprising blades 110 and 112.

For a mixed flow impeller of similar performance, the hub diameter istypically much larger, so that folding into a stored diameter half thedeployed diameter is impossible.

FIGS. 7A and 7B show side and end views of a blade 120 having a winglet122 at the distal end. FIG. 7A shows the distal cross-section of theblade as a dashed line. FIG. 7B shows the winglet moving proximate tothe inner surface of a fluid flow sleeve, a configuration which may beused as a hydraulic bearing for the impeller.

Impellers may have at least one blade having a winglet. In someembodiments, all blades within a blade row include a winglet; otherblades may or may not have a winglet. A winglet can improve hydrodynamicperformance of the impeller. A winglet may also reduce shear stressesthat exist within the fluid, for example reducing degradation ofbiological structures such as cells that may exist within the fluid.

FIGS. 8A-8C show possible winglet configurations. An impeller bladetypically has a pair of opposed faces: a pressure face inducing relativemotion of the fluid through pressure as the blade rotates through thefluid; and a suction face inducing fluid motion by suction. The bladealso has a leading edge cutting though the fluid as the blade rotates, atrailing edge, and an outer edge (which may also be referred to as ablade tip or edge of the distal end of the blade). The winglet issupported by the outer edge or blade tip, which has an airfoil shape. Asshown, the suction side of the blade is on the right, and the pressureside is on the left.

FIG. 8A shows a suction side winglet, the winglet 142 extending from thesuction side of the outer edge of blade 140. This is a view from theleading edge, in cross-section, so that the blade rotates towards thedirection of viewing. FIG. 8B shows a pressure side winglet 146,extending from the pressure face of the blade 144. The parameters may besimilar to the suction side winglet. The function of the pressure sidewinglet is to reduce flow through the gap. There is less effect ofcreating a hydrodynamic bearing, but the pressure side winglet “scrapes”low momentum fluid off the inner surface of the fluid pipe and preventsthis fluid from entering the gap and subsequently being used in the coreof a tip vortex. This can reduce shearing stresses in the bulk of thefluid flow.

FIG. 8C illustrates a combined winglet, extending from both the pressureand suction sides of the outer edge. Embodiments of the presentinvention include the configurations shown in FIGS. 8A-8C. Numericalmethods can be used to design the winglet configurations. Where theblade chord lengths are long and the blade has a significant helicalextent, the geometry and shape of the blade tip and the winglet canbecome complex.

FIG. 8D shows possible winglet edge geometries which may be used. Thefigure shows a radius edge 150, sharp edge 152, and chisel edges 154 and156.

FIGS. 9A-9D further illustrate winglet configurations, the bladesupporting the winglet retaining the same shape in these examples. FIG.9A illustrates the outer edge of a blade 160, not having a winglet.

FIG. 9B shows a pressure side winglet extending the pressure side of theouter blade edge, extending over portion 164. The portion 162 of thewinglet corresponds to the original outer edge area of the blade shownin FIG. 9A.

FIG. 9C shows a suction side winglet, the portion 166 extending from thesuction side of the outer edge of the blade, and the portion 168corresponding to the original outer edge of the blade. In embodiments ofthe present invention, the pressure side of the blade will have a radiusof approximately ⅓ to ½ the blade thickness or width. The extent of thewinglet may be from ½ to 3 times the blade thickness. A thicknessapproximately equal to the blade thickness is shown. The winglet ismostly positioned to the downstream half of the blade as shown. Thepurpose is to create a hydrodynamic bearing where the outer face of thewinglet is in close proximity to the inner surface of the fluid pipe inwhich the blade is operating. Flow in the gap is reduced in strength,and a tip vortex is less likely to form. This reduces shearing stressesin the fluid. The gap can be between approximately 10 to approximately25 percent of the base blade maximum thickness. The gap is a mostlyparallel surface to the pipe of casing. It can be a cylindrical,conical, or curved side cylinder where the radius is a function of theaxial position of the blade element. Parameters for the pressure sideand combined (described below) winglets may be similar.

FIG. 9D shows a combined pressure side and suction side wingletextending from both the pressure face and the suction face of the blade,the portion 170 extending from the pressure face, the portion 174extending from the suction face, and a portion 172 corresponding to theoriginal outer edge of the blade.

The winglets are preferably aerodynamically smooth shapes. The wingletshave leading edges where flows impact the edges of the winglets, andtrailing edges where flow is discharged from the winglet surfaces.Winglets preferably have smooth aerodynamic cross-sections, generally inthe direction of the mean flow, which is parallel to the flow directionalong the blade tip surfaces.

FIGS. 10A and 10B illustrate the provision of an indentation, in thiscase a trench, proximate to the base of a blade. FIG. 10A shows blade180, surrounded by trench 182. The trench is formed in hub 184, and isparallel with and adjacent to the proximal edge of the blade, theproximal edge of the blade extending around the base of the blade whereit joins the hub. FIG. 10B is a sectional view, showing the trench 182and blade 180. The indentation may also be referred to as a “dillet”.

An indentation close to the blade root, such as a trench around some orall of the blade root, can help reduce internal mechanical stresses inthe blades when the blades are in the stored configuration, for examplefolded against the hub. The indentation may also be used to reduce fluidshear stress in the operating state.

FIG. 11 is a photograph of an impeller molded to a configurationaccording to an embodiment of the present invention. The impeller is apolyurethane impeller taken from a mold, having two blades rows of threeblades each.

FIG. 12 is a stress-strain relationship of a non-linear material thatcan be used to form an impeller according to the present invention. Theleft (low stress) and right (high stress) filled circles correspond tothe impeller operating point and storage conditions, respectively. Thestress/strain relationship is approximately linear at the impelleroperating point. The storage condition, where the blades are foldedagainst the hub, is within the high strain non-linear portion of thematerial property curve. This allows the stored configuration to beachieved without passing the material tensile failure point. In exampleimpellers, the maximum material elongation in the stored configurationis approximately 75 percent.

Preferably, a non-linear property material is used for the blades. Theblade material can be relatively stiff at operating loads, and the samematerial relatively flexible at higher strains, for example when theblades are folded in the stored condition. For example, the strain mightbe 10 percent at operating loads and 75 percent while folded, and thestress/strain curve has high modulus (e.g. 10000) at operating loads,and low modulus (e.g. 1000) at higher loads associated with folding. Thestress-strain curve may have two approximately linear regions with abreak point between the operating point and the folded point strains.

FIG. 13 illustrates optimization for fluid shear stress for an exampleimpeller. The distal end of the impeller blade moves proximate to theinterior surface of a cylindrical sleeve, the tip gap between the bladedistal end and the inner diameter of the sleeve being approximately 10to 50 percent of the maximum thickness of the distal end of the blade.

The curve is double normalized, the design point value being 1.0, thescale being read as a factor times the value of stress at the designpoint. For example, FIG. 13 illustrates that making the tip gap smallermakes the shear stress higher, whereas making the gap bigger reduces thestress by a smaller factor. Therefore, the fluid shear stress can bereduced without significantly impacting pumping efficiency.

Impellers according to embodiments of the present invention may becompressed and packaged into a storage sleeve, such as a metal tube,catheter, or other structure, for insertion into an object. For anobject such as a living subject, the diameter of the storage sleeve canbe approximately three to four millimeters, or less. Having inserted thedevice, the impeller can be deployed in situ into a geometry that may beapproximately six to seven millimeters in diameter. The impeller thencan be rotated using a flexible drive shaft coupled to a drive motorexternal to the subject. Impellers according to the present inventioncan be inserted in the stored state, then deployed into an expandedconfiguration (relative to the stored state) and are capable of pumping4 liters per minute, for example, as a medical assist device. In arepresentative example of such a device, the impeller rotates atapproximately 30,000 RPM. The impeller may comprise two or more airfoilshaped blades that form an axial flow pump. The impeller may bepositioned using a guide wire and rotated using a flexible shaft. Theguide wire may run within a hollow center of the flexible shaft, and thehollow center may also convey saline solution or other fluid forinfusion, cooling, and/or lubrication purposes. The guide wire may beremoved, if desired. Implantation into a living subject can be achievedthrough a cannula having a diameter of 3-4 mm, without surgicalintervention. For medical implantation, a drive shaft comprising a metalbraid, or a polymer or composite material braid, can be used, and thedrive shaft diameter may be of the order ½ to 2 millimeters, and may behollow to allow a guide wire to pass through.

In further embodiments, the sleeve has expandable and non-expandableportions. The impeller is stored within the non-expandable portion forinsertion. When the impeller is located at or near the desired location,the impeller is then urged out of the non-expandable portion of thesleeve into the expandable portion. The stored elastic energy within theflexible blades of the impeller induces self-deployment of the impeller,and also the expansion of the expandable portion of the sleeve. Theexpanded sleeve then may have the role of a fluid flow pipe, throughwhich fluid flows when the impeller is rotated. The expandable sleevemay comprise a metal or polymer mesh, or woven fibers, and a smoothsheathing to provide a flexible, expandable tube.

An expandable sleeve may comprise a mesh formed from a flexiblematerial, such as polymers, metals, or other material. In one example,the mesh is made from nitinol, a memory metal alloy. A thin sheet orcylinder of the metal, of a thickness on the order of a thousandth of aninch, is cut using a laser so as to leave a mesh structure.Alternatively, the mesh can be formed from a polymer. Other suitablematerials for the mesh include other metals (such as alloys, includingmemory metal alloy), polymers, and the like. A coating, such an elasticcoating, is then provided over the mesh. For example, an elastic polymersuch as Estane™ can be used, or other polyurethane.

Hence, the expandable sleeve may comprise a mesh, such as a matrix ofwoven wires, or a machined metal cylinder with laser cut voidsrepresenting the spaces between wires, or another material that whendeformed in one direction would elongate in the perpendicular direction.The mesh can then be covered with a thin film of elastane to form afluid flow pipe through which the fluid flows. The mesh can be formed asa cylinder with flow entrance voids at the distal end and flow dischargevoids at the proximal end, the proximal end being closer to the point ofinsertion into an object, such as a pipe or living subject. As thesleeve is shortened in length, for example using a guide wire, thecylinder expands to a greater diameter, allowing a greater flow rate. Ahexagonal cell matrix design, or other design, can be used for the mesh.A coating (for example, biocompatible, corrosion resistant, or flowimproving) can be applied to the sleeve, for example by solutioncasting.

The orientation of the mesh or woven fibers of the sleeve can be chosento allow two stable configurations, stored and deployed. In one example,designed for subject implantation in the stored position, the expandablesleeve in the deployed configuration was approximately 20-30 cm long andthe diameter was approximately 6-7 mm. This diameter allowed for higherfluid flow rate and reduced friction pressure losses. In the storedconfiguration, the expandable portion was elongated by approximately 30percent relative to the deployed configuration, and the diameter wasapproximately 3 mm. The final portion (distal end) of the assemblycomprises a second set of openings and plates, providing an inlet oropening for the influx of fluid to be pumped. The sleeve may alsoprovide a guide wire attachment opening for fluid discharge. A short(such as 1 cm) section of the sleeve may contain linear elements (vanes)arranged about the central axis of the sleeve, through which fluid isdischarged. The vanes may act as stationary stator blades and removeswirl velocity from the impeller discharge flow. The vanes may bemanufactured with airfoil type cross-sections. Applications of animpeller deploying within an expandable sleeve include a collapsiblefire hose with an integral booster pump, a collapsible propulsor, abiomedical pump for a biological fluid, and the like.

The impeller blade can be designed so as to minimize destruction ofdelicate particles (such as emulsion droplets, suspensions, biologicalstructures such as cells, and the like) within a fluid. A CFD model wasused to simulate the shear stresses experienced by particles passingthrough a simulated impeller. Time integrations of intermediate shearstresses experienced by the particles were used to provide an estimatedprobability of cell destruction in a biomedical application. A splitblade design, in which there are a plurality of blade rows such asdiscussed above, reduces the residency time that cells remain inintermediate shear stress regions, allowing an advantageous reduction incell or other particle destruction compared with conventional impellerdesigns.

Impeller blades may, for example, occupy as much as 95% of thecompressed volume of the impeller when the impeller is in the storedstate. The blades may be formed from a rubbery, elastic, or otherresilient material that has sufficient resilience to expand when ejectedfrom a sleeve. In other examples, the blades may be formed from otherflexible polymers, an expandable foam optionally with a skin, or othercompressible or deformable materials including metals.

Impellers according to embodiments of the present invention may havemultiple separate sets of blades, rather than a long, continuous, spiralblade. Prior art impellers typically have a continuous long helicalblade that is difficult to fold up against the hub. By splitting a longblade into two or three shorter sections, the blade can be more easilyfolded into a cylindrical volume or space and subsequently deployed whenproperly located. The number of blade rows can be one, two, three, four,five, or higher. The twist pitch angles may be variable.

One approach to impeller design provides a two blade impeller withblades exhibiting a significant degree of wrap around the central hub.However, the three-dimensional shape of the blades limits the degree towhich they can be folded without deforming or breaking. By breaking asingle blade row into two, three (or possibly more) rows of blades thatexhibit minimum wrap around the hub, the blades have a moretwo-dimensional shape, allowing easier bending during the storageprocess. The combination of three or two blade rows can produce the sameflow and pressure as a single blade row. An axial pump was designed withtwo blade rows, and CFD (computational fluid dynamics) analysisindicated that this pump design was adequate for use in a medical assistapplication. A model was constructed of a flexible polyurethane materialand successfully folded into a metal sleeve.

Impellers can be used with flows of very small Reynolds number, forexample, the pumping of relatively viscous fluids at low velocity orflow rate. Very small impeller pumps, on the order of 6 mm diameter, maybe fabricated from a polymer and extracted from a precision mold. Thisallows production of impellers at very low cost. The use of polymerblades allows the pump impellers to be extracted from molds withoutbecoming mold-locked, and allows the use of one-piece molds, instead ofmulti-part or split molds. This can be advantageous for pumping smallquantities of bio-fluids. Impellers may be used for flows of typicalReynolds numbers as well. Impeller diameters can also be in the range ofseveral inches to several feet.

Applications of the improved impeller designs described include pumpsfor chemical engineering, propellers for airborne or maritime vessels,water pumps, and the like. Improved impeller designs are useful for anyapplication where an impeller is to be stored in a compactconfiguration. Impellers may be formed from metal sheets, plastic, andnon-resilient materials, for example, in foldable configurations.Deployment may include the use of motors or other mechanical devices tounfold blades, automatic deployment induced by centrifugal forces, andthe like. Examples of the present invention include a device locatableinside a subject so as to pump a fluid, the device being inserted intothe subject in an insertion configuration having an insertioncross-section, the device operating inside the subject in an operatingconfiguration having an operating cross-section, wherein the operatingcross-section is greater than the insertion cross-section.

The operating diameter (of the largest circle swept out by the outeredge of the impeller blade as it rotates) may be over 50% greater thanthe insertion diameter of the impeller, and may be over 100% greaterthan the insertion diameter.

The invention is not restricted to the illustrative examples describedabove. Examples are not intended as limitations on the scope of theinvention. Methods, apparatus, compositions, and the like describedherein are exemplary and not intended as limitations on the scope of theinvention. Changes therein and other uses will occur to those skilled inthe art. The scope of the invention is defined by the scope of theclaims.

Patents, patent applications, or publications mentioned in thisspecification are incorporated herein by reference to the same extent asif each individual document was specifically and individually indicatedto be incorporated by reference.

1. An apparatus for inducing motion of a fluid relative to theapparatus, the apparatus comprising: an impeller, including: a hubextending in a length direction; and a plurality of blades supported bythe hub, each blade having a proximal end attached to the hub and adistal end; the blades being arranged in at least two blade rowsarranged in series in the length direction of the hub; the impellerhaving a deployed configuration and a stored configuration, each bladein the deployed configuration of the impeller extending away from thehub, and at least one of the blades in the stored configuration of theimpeller being compressed so as to move the distal end of the at leastone blade towards the hub.
 2. The apparatus as claimed in claim 1,wherein each blade row includes at least two blades.
 3. The apparatus asclaimed in claim 1, wherein the distal end of at least one of theplurality of blades includes a winglet.
 4. The apparatus as claimed inclaim 1, wherein the distal end of each blade in at least one blade rowincludes a winglet.
 5. The apparatus as claimed in claim 1, wherein thedistal end of each of the plurality of blades includes a winglet.
 6. Theapparatus as claimed in claim 1, wherein the plurality of blades areformed integrally with the hub.
 7. The apparatus as claimed in claim 1,wherein the impeller has a first radius in the deployed configurationand a radius in the stored configuration which is less than half thefirst radius.
 8. The apparatus as claimed in claim 1, further comprisingan expandable sleeve including a matrix and a film disposed around thematrix, at least part of the impeller being located within the sleeve.9. The apparatus as claimed in claim 8, wherein the matrix is formedfrom a shape memory material.
 10. The apparatus as claimed in claim 8,wherein the film includes an elastic polymer.
 11. The apparatus asclaimed in claim 8, wherein the expandable sleeve has a storageconfiguration and an expanded configuration, the sleeve in the storageconfiguration having a diameter less than about 4 mm.
 12. The apparatusas claimed in claim 8, wherein the expandable sleeve has an inlet endand a discharge end, the sleeve including a plurality of vanes arrangedat the discharge end.
 13. The apparatus as claimed in claim 12, whereineach of the plurality of vanes has an airfoil-shaped cross-section. 14.An apparatus for inducing motion of a fluid relative to the apparatus,the apparatus comprising: an impeller, including: a hub extending in alength direction; and a plurality of blades supported by the hub, eachblade having a proximal end attached to the hub and a distal end; theblades being arranged in at least two blade rows arranged in series inthe length direction of the hub; the impeller having a deployedconfiguration, a stored configuration, and an operational configuration,each blade in the deployed configuration of the impeller extending awayfrom the hub, at least one of the blades in the stored configuration ofthe impeller being compressed so as to move the distal end of the atleast one blade towards the hub, and at least some of the blades in theoperational configuration being deformed from the deployed configurationupon rotation of the impeller when in the deployed configuration. 15.The apparatus as claimed in claim 14, wherein the impeller has a firstradius in the deployed configuration and a second radius in the storedconfiguration which is less than half the first radius.
 16. Theapparatus as claimed in claim 15, wherein the impeller has a thirdradius in the operational configuration, the second radius being lessthan half the third radius.
 17. The apparatus as claimed in claim 14,wherein the impeller in the operational configuration is operable topump about 4 liters of fluid per minute.